This invention relates to a one-way clutch that effects and blocks torque transmission between inner and outer rings by shifting intermediate members according to the direction of relative rotation between the inner and outer rings, and particularly relates to improvement of a spring member for pressing and urging each of the intermediate members into the shift in a direction to wedge between the inner and outer rings.
As for example disclosed in Japanese Unexamined Patent Publication No. 61-228153, it is known that in a belt type auxiliary equipment driving apparatus for a vehicle engine, a one-way clutch is disposed, in order to transmit torque of a crank shaft revolving with angular velocity variations due to an explosion stroke of the engine to input shafts of auxiliary equipment through a belt, in a torque transmission path so that for a period of increase in angular velocity during the angular velocity variations torque transmission is effected between the crank shaft and the input shafts of the auxiliary equipment to drive the input shafts into rotation, while for a period of decrease in angular velocity during the angular velocity variations the torque transmission is blocked to avoid torque due to moment of inertia of the input shafts from being transmitted to the crank shaft whereby load placed on the belt is reduced to provide elongated belt life.
Now, the operation of the above one-way clutch will be described. As shown in FIG. 10, each of intermediate members c is retained by a cage d between inner and outer rings a and b for clockwise and counterclockwise rocking motion in the figure and is normally pressed clockwise in the figure by a flat spring e as a spring member to wedge between the inner and outer rings a and b. For the period of increase in angular velocity, for example, when the outer ring b relatively rotates in its locking direction (clockwise in the figure) with respect to the inner ring a, the relative rotation causes each intermediate member c to wedge between the inner and outer rings a and b thereby effecting torque transmission between the inner and outer rings a and b. On the other hand, for the period of decrease in angular velocity, when the outer ring b relatively rotates in its idling direction, the relative rotation causes each intermediate member c to rock opposite to the direction to wedge between the rings against the pressing force of the flat spring e. This produces slippage between each intermediate member c and the inner and outer rings a, b thereby blocking torque transmission.
As the spring member, a coil spring is generally used apart from the above-mentioned flat spring e. A comparison of both the springs indicates that the coil spring is more suitable in durability. Here, description will also be made about the structure of the one-way clutch when the coil spring is used as the spring member. As shown in FIGS. 11 and 12, out of a pair of circumferentially opposed wall surfaces of each retaining hole g of the cage d, the wall surface on the opposite side to the wall surface of a protruding wall for supporting the intermediate member c to allow its rocking motion (left-hand side in FIG. 12) is formed with a recess h and the root end of the coil spring f (left end in FIGS. 11 and 12) is accommodated in the recess h. It is to be noted that the root end of the coil spring f is generally closely wound, though its illustration is omitted.
Meanwhile, in the one-way clutch, torque transmission is started not at a point in time when the angular velocities of the inner and outer rings a and b are coincident with each other for the period of increase in angular velocity but slightly behind the point in time. If this is described using the above case as an example, torque of the outer ring b is started to be transmitted to the inner ring a at a point in time when the outer ring b is further increased in angular velocity to relatively rotate by a certain angle with respect to the inner ring a after the angular velocity of the outer ring b has been increased for the period of increase in angular velocity until it matches the angular velocity of the inner ring a. The relative angle between the inner and outer rings a and b at the point in time is called xe2x80x9ca delay anglexe2x80x9d. If the delay angle is too large, excellent response to an angular velocity variation cannot be attained and therefore proper torque transmission cannot be provided.
The reasons for the occurrence of the delay angle are not only that each intermediate member c essentially requires a certain time to rock to wedge between the inner and outer rings a and b due to relative rotation of the inner and outer rings a and b in the locking direction but also that each intermediate member c vibrates due to angular velocity variations. Namely, when each intermediate member c vibrates, slippage occurs between the intermediate member c and each of the inner and outer rings a and b even if the inner and outer rings a and b relatively rotate in the locking direction, and therefore its wedging movement between the inner and outer rings a and b is further delayed so that the intermediate member c cannot follow an angular velocity variation.
Further, the frequency of angular velocity variations of the vehicle engine is low at low engine speeds and high at high engine speeds. For example, in a four-cycle four-cylinder engine involving two explosion strokes for one revolution of the crank shaft, the frequency of angular velocity variations reaches 100 to 200 Hz at high engine speeds where the speed of the crank shaft reaches 3000 to 6000 rpm.
Accordingly, in order to attain excellent response to angular velocity variations in the entire speed range of the vehicle engine, it is necessary to allow each intermediate member c to sufficiently follow high-frequency angular velocity variations at high engine speeds. To satisfy this requirement, the spring member must have a large spring constant enough to suppress variations of the intermediate member c due to such high-frequency angular velocity variations.
Problems to be Solved
However, the conventional one-way clutch using the coil springs f as the spring members generally has the disadvantage of a lower spring constant of the coil spring f as compared with the flat spring e of equal size in its operating direction. As can be seen from this point, the coil spring f is excellent in durability over the flat spring e, whereas the one-way clutch using the coil spring f has a problem of the difficulty in attaining excellent response to high-frequency variations as described above as compared with the one-way clutch using the flat spring e. In this case, if the spring constant is increased by increasing the size of each coil spring f in the operating direction, the one-way clutch will be greater. This causes a new problem of the difficulty in disposing the one-way clutch in an engine room of the vehicle.
Further, the conventional one-way clutch using the coil springs f has another problem. Specifically, as shown with exaggeration in FIG. 13, the root end of the coil spring f has a tendency to easily extrude from the recess h toward the outer ring b as a result of relative rotation between the inner and outer rings a and b. Further, if expansion and contraction of the coil spring f itself resulting from rocking motion of the intermediate member c is added to this tendency, the distal end (right end in FIG. 14) of the coil spring f is also displaced toward the outer ring b as shown with exaggeration in the figure. Furthermore, since the rotation of the coil spring f itself around the axis of the coil also concurs, these events results in easily providing an unstable pressing force on the intermediate member c. This also invites insufficient suppression of the above-mentioned vibrations of the intermediate member c.
The present invention has been made in view of the foregoing points and therefore a major object of the present invention is to obtain, in using coil springs as spring members for a one-way clutch into which torque accompanied with high-frequency angular velocity variations is input, a high spring constant equivalent to the case of using flat springs even if the size of the coil spring in its operating direction is not increased, thereby providing a one-way clutch having excellent response to input torque accompanied with high-frequency angular velocity variations and excellent durability.
The present invention takes the following measures to solve the above problems.
A first inventive measure is directed to a one-way clutch comprising: an inner ring; an outer ring disposed coaxially around an outer periphery of the inner ring and assembled relatively rotatably with the inner ring; a cage disposed between the inner and outer rings for relative rotation with respect to the inner and outer rings; a plurality of intermediate members that are each retained in the cage so as to be changeable in position in a plane orthogonal to the axis of the inner and outer rings, change the position thereof to wedge between the inner and outer rings upon relative rotation of the inner and outer rings in a locking direction to effect torque transmission between the inner and outer rings, and change the position thereof opposite to the direction of wedging between the inner and outer rings upon relative rotation of the inner and outer rings in an idling direction to block torque transmission between the inner and outer rings; and a plurality of spring members, disposed correspondingly to the intermediate members in the cage, for pressing the corresponding intermediate members to wedge the intermediate members between the inner and outer rings.
Each of the spring members includes: a plurality of coil springs that are juxtaposed to align in an axial direction of the inner and outer rings and extend in a direction to press the corresponding intermediate member, are retained at one ends thereof by the cage and resiliently contact at the other ends thereof with the intermediate member; and a connecting portion for connecting the one ends of the plurality of coil springs together.
In this inventive measure, since each of the spring members of the one-way clutch includes the plurality of coil springs juxtaposed with respect to the corresponding intermediate member, the entire spring constant of the spring member is obtained by summing up spring constants of the coil springs. Accordingly, even if the natural length of each coil spring is not increased, the spring constant of the spring member on the intermediate member becomes large as a whole.
Further, since the one ends of the coil springs are connected together through the connecting portion, each coil spring is restrained against rotation around the coil axis and when each coil spring is retained at its one end by the cage, the other end of the coil spring is easily fixed using the connecting portion. Accordingly, each coil spring makes its pressing conditions against the intermediate member steady and therefore the pressing force on the intermediate member is also stabilized. Furthermore, since the plurality of coil springs are formed integrally through the connecting portion, increase in number of components can be avoided in spite of use of the plurality of coil springs for each intermediate member.
In a second inventive measure, when the number of coil springs provided in each of the spring members is two in the first inventive measure, the two coil springs and the connecting portion of each of the spring members are formed of a single wire.
With this inventive measure, since the two coil springs and the connecting portion are formed of a single wire, the connection of both the coil springs through the connecting portion can be made optimally.
In a third inventive measure, the end of a wire forming the other end of the coil spring in the first and second inventive measures is formed to avoid contact with the inner and outer rings.
With this inventive measure, when torque is input to the one-way clutch to rotate the cage, in some cases attendant centrifugal forces or a position change of the intermediate member may change the position of the other end of the coil spring in a radial direction of the inner and outer rings. In this case, since the wire end forming the other end of the coil spring does not contact with the inner and outer rings, there can be obviated the occurrence of events due to engagement of the wire end with the inner and outer rings, i.e., an event that the operation of the coil spring is blocked or an event that the contact surfaces of the inner and outer rings with the intermediate member are damaged to adversely affect the position change of the intermediate member.
In a fourth inventive measure, the one-way clutch in the first to third inventive measures is disposed in a torque transmission path for transmitting torque of a crank shaft revolving with angular velocity variations due to an explosion stroke of a vehicle engine to an input shaft of auxiliary equipment through a power transmission belt.
With this inventive measure, torque accompanied with angular velocity variations due to the explosion stroke of the vehicle engine is input to the one-way clutch in the torque transmission path in which torque of the crank shaft of the vehicle engine is transmitted to the input shaft of the auxiliary equipment through the power transmission belt. Therefore, each intermediate member vibrates due to the angular velocity variations. Particularly for a four-cylinder four-cycle engine, the frequency of angular velocity variations is a high frequency in the range of 100 to 200 HZ at high engine speeds of 3000 to 6000 rpm. Accordingly, excellent properties of the spring member in the first to third inventive measures can be exhibited specifically and properly.
In a fifth inventive measure, based on the fourth inventive measure, the inner ring is provided to be connectable with one of the crank shaft of the vehicle engine and the input shaft of the auxiliary equipment, and the outer ring is provided with a pulley section for training the power transmission belt therearound to rotate unitarily with the outer ring.
With this inventive measure, when the one-way clutch is disposed in a belt type auxiliary equipment driving apparatus for an vehicle engine, the inner ring is connected to the crank shaft of the vehicle engine or the input shaft of the auxiliary equipment and the power transmission belt is trained around the outer ring. In this case, since the outer ring is provided unitarily rotatably with the pulley section for training the power transmission belt thereover, disposition of the one-way clutch in the belt type auxiliary equipment driving apparatus is facilitated.
Effects of Invention
According to the present invention, in a one-way clutch which has a plurality of intermediate members for changing their positions in a direction to wedge between inner and outer rings when the inner and outer rings relatively rotate in a locking direction and changing their positions opposite to the direction to wedge between the inner and outer rings when the inner and outer rings relatively rotate in an idling direction and in which the intermediate members are pressed by corresponding spring members to change their positions in the direction to wedge between the inner and outer rings, each of the spring members includes: a plurality of coil springs that are juxtaposed with respect to the intermediate member, are retained at one ends thereof by a cage and resiliently connect at the other ends thereof with the intermediate member; and a connecting portion for connecting the plurality of coil springs together. Therefore, the entire spring constant of the spring member can be increased even if the size of each coil spring in its operating direction is not increased, each coil spring can be restrained against rotation around the coil axis, and each coil spring can be fixed at its one end with the use of the connecting portion. Accordingly, even on receipt of a centrifugal force or vibration due to high-speed rotation, each coil spring can make its pressing conditions against the intermediate member steady thereby providing a stable pressing force of each coil spring. Further, integral configuration of the plurality of coil springs can avoid increase in number of components due to use of the plurality of coil springs for each intermediate member.
According to the second inventive measure, when the number of coil springs for each spring member is two, the two coil springs and the connecting portion are formed of a single wire. Therefore, the two coil springs can be optimally connected together in one piece.
According to the third inventive measure, since the wire end at the other end of each coil spring resiliently contacting with the intermediate member is provided to avoid contact with the inner and outer rings, there can be obviated the occurrence of events due to engagement of the wire end with the inner and outer rings, i.e., an event that the operation of the coil spring itself is blocked or an event that the contact surfaces of the inner and outer rings with the intermediate member are damaged.
According to the fourth inventive measure, since the one-way clutch is used for a belt type auxiliary equipment driving apparatus for a vehicle engine frequently producing high-frequency vibrations, this properly provides the effects of the inventive measure of claim 1.
According to the fifth inventive measure, since the pulley section for training the power transmission belt therearound is provided around the outer ring so that the one-way clutch can be used as a one-way clutch-integrated pulley, the one-way clutch according to the present invention can be readily disposed in the belt type auxiliary equipment driving apparatus for a vehicle engine.